Varactor tuning system

ABSTRACT

A television channel selector includes UHF and VHF tuners each having a varactor as the frequency-determining element. A number of fixed contacts on a rotary switch are respectively associated with different channels in both the VHF and UHF regions of the spectrum; also included on the switch are a pair of selection contacts. Printed on the same substrate which carries the switch contacts are a plurality of resistors which together constitute a voltage divider that has individually different junctions between the resistors connected to respective different ones of the fixed contacts. A fasttuning shaft drives the selection contacts over the fixed contacts. That shaft is detented each time the selection contacts are moved over a chosen number of the fixed contacts. A slow-tuning shaft is coupled through a gear system to the fast-tuning shaft. The slow-tuning shaft is detented in rotational increments that correspond to movement of the selection contacts, through the gear system and the first shaft, from each one of the fixed contacts to the next. The selection contacts read out a voltage from the divider which is fed to the varactors in determination of frequency. For fine tuning, the varactor control voltage is derived from a tap on a potentiometer the opposite ends of which are connected by the selection contacts across selected individual different ones of the resistors in the voltage divider.

United States Patent [191 Hendrickson [451 Sept. 16, 1975 1 VARACTORTUNING SYSTEM Melvin C. Hendrickson, Elmhurst, Ill.

[73] Assignee: Zenith Radio Corporation, Chicago,

221 Filed: Sept. 23, 1974 211 Appl. No.: 508,138

Related US. Application Data [62] Division of Ser. No. 331,921, Feb. 12,1973, Pat. No.

[75] Inventor:

[56] References Cited UNITED STATES PATENTS 3,678,421 7/1972 Ono 334/153,868,609 2/1975 Koyangi 334/1 1 Primary Examiner-Robert L. GriffinAssistant Examiner-Marc E. Bookbinder Attorney, Agent, or Firm-NicholasA. Camasto ABSTRACT A television channel selector includes UHF and VHFtuners each having a varactor as the frequencydetermining element. Anumber of fixed contacts on a rotary switch are respectively associatedwith different channels in both the VHF and UHF regions of the spectrum;also included on the switch are a pair of selection contacts. Printed onthe same substrate which carries the switch contacts are a plurality ofresistors which together constitute a voltage divider that hasindividually different junctions between the resistors connected torespective different ones of the fixed contacts. A fast-tuning shaftdrives the selection contacts over the fixed contacts. That shaft isdetented each time the selection contacts are moved over a chosen numberof the fixed contacts. A slow-tuning shaft is coupled through a gearsystem to the fasttuning shaft. The slow-tuning shaft is detented inrotational increments that correspond to movement of the selectioncontacts, through the gear system and the first shaft, from each one ofthe fixed contacts to the next. The selection contacts read out avoltage from the divider which is fed to the varactors in determinationof frequency. For fine tuning, the varactor control voltage is derivedfrom a tap on a potentiometer the opposite ends of which are connectedby the selection contacts across selected individual different ones ofthe resistors in the voltage divider.

7 Claims, 9 Drawing Figures Reg. B+ 163183 153 UHF 178 Tune F m- 161Switch- J 160 20 and l I F Resistor 152 r Network TYJEZI" 156 I f 1s5Control Network. 1e5

PATENTEDSEP 1 6l975 3. 906.373

SHEET 2 BF 100 83 I I 104 l l FIG.2 100,17 16 105 106 Channel 8 Se|ector118 PATENIEBSEP 181915 31905373 sum 3 BF IGB 21 Reg.B+ 163183 /182 153UHF f 17s 24 Switch- 18 and Resistor 152 K Network WP 156 1 Tuner 1 17o1 '22 150 186 Control Network 1s5 PATENTEU 'SEF 1 s 1915 sumuujg FIG.5b

2o2: T g 192? 232; 18%

l 210 5d. FIG. 5c

FIG.5Cl

FIG.5d

FIG.5e

VARACTOR TUNING SYSTEM Related Application This application is adivision of application Ser. No. 331.921, filed Feb. 12, 1973, andassigned to the as signee of this application now US. Pat. No. 3878466.

BACKGROUND OF THE INVENTION The present invention relates to televisionchannel selectors. More particularly, it pertains to electricalcircuitry and mechanical apparatus capable of selecting channels in boththe UHF and VHF regions of the television spectrum.

A typical television tuner or channel selector includes a radiofrequency amplifier, a local oscillator and a. mixer for heterodyningthe received radio frequency signal with the local oscillator signal todevelop a fixed intermediate frequency signal which then is processed toyield the necessary image and sound reproduction information. With thisapproach, it is necessary that both the radio frequency amplifier andthe local oscillator be tunable over a range of frequencies in order tobe able to receive all of the different television channels. With theexpansion of commercial television broadcasting from the very highfrequency (VHF) spectrum into the ultra-high frequency (UHF) spectrum,the required tuning range was greatly increased. Tuning usually has beenaccomplished by using two separate tuners, one for channels in the VHFspectrum and the other for channels in UHF spectrum. In most instances,each tuner has been provided with its own knob or dial for manipulationby the user. Thus. the VHF knob enables selection from among VHFchannels 213, while the UHF knob is employed to select from among UHFchannels 14-83. Because of the substantially larger number of UHFchannels, however, the ease or accuracy of selection ofa particular UHFchannel often is inferior as compared with selection ofa particular VHFchannel.

OBJECTS OF THE INVENTION It is, accordingly, a general object of thepresent invention to provide a television channel selector whichfeatures improved ease and accuracy of use in selecting particulardifferent channels.

Another object of the present invention is to provide a combined UHF andVHF channel selecting system in which access to different adjacent onesof both the UHF and VHF channels is achieved by manipulation of the sametuning knob.

A further object of the present invention is to provide a televisionchannel selector which takes advantage of the attributes of printedcircuitry in achieving switch selection between different channels.

Still another object of the present invention is to provide a televisionchannel selector which includes a single fine tuning control for allchannels in both the VHF and UHF spectra.

SUMMARY OF THE INVENTION A combined UHF and VHF television channelselector constructed in accordance with the present invention includestuning means having at least one varactor as the frequency determiningelement with the fre quency determined being. a function of the voltagepresented to a terminal of the varactor. A rotary switch features apredetermined number of fixed contacts re spectively associated withdifferent channels in both the VHF and UHF spectrum together with atleast one selection contact that is movable over respective differentones of the fixed contacts. A plurality of resistors are seriesconnected to form a voltage divider, and individually progressivedifferent junctions between'the resistors are connected with respectivedifferent ones of the fixed contacts. For fast-tuning, a first rotatableshaft is coupled to the selection contact in order to drive the samesuccessively over the fixed contacts. The first shaft is detented eachtime upon movement of the selection contact successively over a chosennumber of the fixed contacts. A slow-tuning means includes a secondshaft which is mechanically coupled to the first shaft by a gear system.The second shaft also is detented, but in rotational incrementscorresponding to movement of the selection contact, through the gearsystem and the first shaft, from each one of the fixed contacts to thenext. Finally, the arrangement includes means for coupling the selectioncontact to the varactor terminal in order to control the frequencydetermining voltage. Also featured is a fine tuning means which includesa potentiometer that has a movable tap coupled to the varactor terminalin order to supply the frequency determining voltage. The channelselection means includes a coupling of the opposing ends of thepotentiometer selectively across different individual ones of theresistors in order to adjust the level of the frequency determiningvoltage in correspondence with changes in channels.

BRIEF DESCRIPTION OF THE DRAWINGS The features of this invention whichare believed to be novel are set forth with particularity in theappended claims. The invention, together with further objects andadvantages thereof, may best be understood, however, by reference to thefollowing description taken in conjunction with the accompanyingdrawings, 'in the several figures of which like reference numeralsidentify like elements, and in which:

FIG. 1 is a schematic diagram of a combined UHF and VHF televisionchannel selector;

FIG. 2 is a schematic diagram of a switching arrangement used in thetuner of FIG. 1;

FIG. 3 is a diagrammatic plan viewof a rotary-switch contact arrangementwhich incorporates the circuitry shown in FIG. 2;

FIG. 4 is a schematic diagram which includes a mechanical drive systemfor tuning the selector of FIG. 1;

FIG. 5a is a side elevational view of an alternative mechanical drivingarrangement;

FIG. 5b is a front elevational view of an indicator dial utilized in thearrangement of FIG. 5a; FIG. 5c is a fragmentary cross sectional view ofa portion of the arrangement of FIG. 5a;

FIG. 5d is a fragmentary view of a portion of the apparatus in FIG. 50as taken along the line 5d5d in that Figure; and

FIG. Se is another fragmentary cross sectional view of a portion of theapparatus shown in FIG. 5c.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT As illustrated in FIG.1, a television channel selector includes a VHF tuner 20 and a UHF tuner21. The primary frequency determining element in each of tuners 20 and21 are respective varactors 22 and 24. Having ,already found commercialutilization, varactor tuned to note that each varactor exhibits a changein capacitance in response to variations in a potential presentedacrossitstwo terminals. Since the capacitance of the varactor iscombined with a fixed inductance to constitute a tuning circuit thepoint of resonance of which establishes the operating frequency of theassociated circuitry, variation in the value of the capacitance servesto tune that circuitry to different frequencies. In this instance, oneterminal of each of varactors 22 and 24 is connected to ground asindicated, so that it is a voltage presented to the other terminal ofeach varactor which-determines the frequency of operation. In thespecific .case of tuners 20 and 21, the function controlled by jthe,respective varactors is the local oscillator frequency of, thevsuperheterodyne type tuning arrangernent Of course, the output of eachtuner is a fixed intermediate frequency television signal which then ishave allocated different ranges or bands in the fre- -quency spctrumfortelevision usage. A first band extends from 54 to.'7,2 megahertz and isfurther divided into successive individual channels each having a widthof 6 megahertz. This band accommodates channels 2 through 4. The secondband embraces 76 to 88 megahertz, accommodating channels and 6. Assignedthe range of 174 to 216 megahertz is a third band which similarlyaccommodates channels 7 through 13. All three of the aforementionedbands are denominated as being in the very high frequency or VHF portionof the spectrum. Finally, a fourth band has been assigned in what istermedthe ultra high frequency or UHF portion of they-spectrum. Thisband extends from 570 to 890 megahertz and is subdivided into channels14 to 83.

Because of the wide separation in frequency as between the first andsecond bands, on the one hand, and the third band on the other, it hasbeen customary in the design of many VHF tuners to provide a band switchto make a coarse adjustment in its operating frequency when switchingbetween channels 6 and 7. Thus, tuner is associated with a first switch26 which is operated by suitable cams on a channel selector 27 toconnect a source of potential B+ along one path to tuner 20 during theselection of any of channels 2 through 6. On the other hand, selector 27closes a switch 28 to connect source B+ as an energizing -poten tial totuner 20 over another path when selecting any of channels 2 through 13.A bias potential from a source C is connected to tuner 20 in the firstmentioned path through a resistor 29. When switch 26 is closed, the B+potential as applied to the tuner is effectively reduced in value by theC- potential and thereby impresses a comparatively low positive voltageon tuner 20 to maintain operation of the'tuner in one of channels 2-6.

Connected to the junction between switch 28 and tuner 20 is the emitterof a transistor 30, the collector of which is returned to ground througha resistor 31. A bias resistor 32 is connected between the collector andbase of transistor 30. The potential appearing across resistor 31 is fedfrom the collector of transistor 30 to the base of a second transistor34 which has its emitter connected to the BF potential source. ltscollector is connected into tuner 21 in order to provide its primaryoperating potential. When switch 28 is closed, a positive potentialappears at the emitter of transistor 30 as a result of which the voltageat the top of resistor 31 is sufficient to cut off operation oftransistor 34 and UHF tuner 21 is thereby disabled. On the other hand,when 7 switch 28 is open so as to disable VHF tuner 20, transistor 34 isin an on condition and thereby connects the B+ energizing potential totuner 21.

Control voltage is supplied to varactor 22 over a lead 36, while a lead38 conveys control voltage to varactor 24. Leads 36 and 38 are shuntedto ground by respective filter capacitors 40 and 42. Moreover, lead 36connects to one comer 43 of a bridge 44, and lead 38 connects to adiagonally opposite corner 45 of the bridge. The bridge itself iscomposed of resistors 46, 4 7,,4,8 and 49 which constitute its fourdifferent arms, respectively. Another corner 50 of bridge 44 isconnected to a tap 52 on a potentiometer 53. The opposite ends ofpotentiometer 53 are connected to respective switch contacts 54 and 55.Spaced alongside contact 54 are a succession of separate switch contacts58, 59, and 61. On the other hand, spaced alongside contact 55 isanother series of contacts 63, 64, 65, 66 and 67. Associated withcontacts 63-67 is a voltage divider composed of a plurality of resistors71, 72, 73, 74 and connected in series between ground and a source ofregulated B+ potential. Contacts 63-67 are individually connected torespective different junctions be tween successive ones of resistor7l-75. Also, contacts 58-61 are individually stagger-connected torespective different ones of contacts 64-67. That is, contact 58 isconnected to contact 64, contact 59 is connected to contact 65, andcontact 61 is connected to contact 67. The dashed lines joining contacts60. and 66, like the dashed lines in the center portion of voltagedivider 70, serve to indicate the existence of additional andsimilarly-arranged contact pairs and voltage divider resistors. Finally,a pair of movable switch contacts 78 and 79 serve individually toconnect respective contacts 54 and 55 to selected correspondingdifferent ones of contacts 58-61 and 63-67. The movement of contacts 78and 79 is effected by channel selector 27.

The staggered interconnections and the physical orientation is such thatat any one position movable contacts 78 and 79 serve to connect theopposite ends of potentiometer 53 across aparticular one of resistors71-75. Thus, as movable contacts 78 and 79 connect to fixed contacts onthe voltage divider further from ground, the voltage range acrosspotentiometer 53 becomes correspondingly higher, Consequently, thevoltage presented to bridge 44 from potentiometer tap 52 is increasedwhereupon the voltage presented to varactors 22 and 24 similarly isincreased. At the same time, and for any particular setting of movablecontacts 78 and 79, adjustment of the position of tap 52 onpotentiometer 53 serves as a finer adjustment of the voltage levelultimately presented to varactors 22 and 24. Thus, by suitableproportioning of the values of resistors 71-75 in the voltage divider,movable contacts 78 and 79 serve to successively select a plurality ofdifferent channel-representative potentials, while potentiometer 52serves during selection of any one particular channel as a fine tuningcontrol.

Connected to the final corner 80 of bridge 44 is a potential derivedfrom an automatic frequency control (AFC) circuit 81 and suppliedthrough abalanced network 82. More particularly, network 82 includes apair of transistors 83 and 84 with the collector of transistor 83connected to the B+ source through a resistor 85. The collector oftransistor 84 is connected through a diode 87 to a low voltagealternating current source A and also is shunted to ground by a filtercapacitor 88. The automatic frequency control signal from circuit 81 isfed through a resistor 90 in common to the bases of both transistors 83and 84. A filter capacitor 91 cou ples the terminal output of circuit 81to ground. Connecting the emitters of transistors 83 and 84 are a pairof series connected resistors 92 and 93, with the junction between thosetwo resistors being directly connected to corner 80 of bridge 44.

In the conventional manner, AFC circuit 81 responds to frequencydepartures in the received signal, typically by detecting a portion ofthe intermediate frequency signal in the television receiver, anddevelops a control voltage which is applied, in this case through bridge44, to varactors 22 and 24 in order to compensate or neutralize thatchange in frequency.

A preferred arrangement of voltage divider 70 and its associatedcontacts and other connections is depicted in FIG. 2. A plurality offixed contacts 100 are spaced one after another in a column and arearranged to permit selection of any of channels 2 through 83. As shown,each individual contact is numbered with the channel or channels withwhich it is associated. The two contacts at either end, respectively,are associated with but a single channel and hence bear the numbers 2and 82, respectively. All of the remaining contacts are each associatedwith two different adjacent channels; thus, the second contact from thebottom is denominated as being associated with both channels 3 and 2.Moreover, it will be noted that each contact is associated with the samechannel as is an immediately adjacent contactv Thus, the second andthird contacts from the bottom are both associated with channel 3. Inaddition, the contacts respectfully associated with channels 4-5, 6-7and 13-14 are split into two electrically isolated segments or sections.Of course, the dashed lines joining the contact associated with channels16-17 and the contact associated with channels 82-83 indicate fordrawing convenience the inclusion of a plurality of additional contactsspaced successively in that region and respectively associated withchannels 17 to 82.

In the arrangement of FIG. 2, voltage divider 70 is divided into twoportions. A first portion extends between a source of potential 8+ andground and includes, in successive series combination, resistors102-109. The associated contacts, for channels 14-83, are individuallyconnected to respective differentjunctions between successive differentones of those resistors. The second portion of divider 70 is composed,again in successive series combination, of a plurality of resistors112-127 with that combination of resistors again extending between asource of potential 8+ and ground. It will be noted that resister 120bridges the split contact associated with channels 6 and 7, whileresistor 123 simply bridges the split contact associated with channels 4and 5. The reason those contacts are split and the additional bridgingresistances are included is the need for an extra voltage incrementbetween channels 4 and 5 and between channels 6 and 7 to accommodate theextra frequency difference that exists between those two pairs ofchannels. This is the same frequency difference mentioned above asoccurring between the first and second and the second and third bands ofthe frequency spectrum assigned to television usage. The use of the twoseparate voltage divider portions accommodates'the similarly abrupt stepin frequency that occurs in going from channel 13 to channel 14 whichcorresponds to changing from the third band to the fourth band mentionedabove.

For selection of any particular channel, the opposite ends ofpotentiometer 52 are respectively connected to two different contactswhich in this case are adjacent and which serve, as in the case ofdivider in FIG. 1, to cause potentiometer 52 to be connected across anindividual dividing resistor in the voltage divider. Thus, movable tap52 on potentiometer 53 again serves as a fine tuning control, and theoutput from that tap is shown in this case as being connected to oneterminal of varactor 20 so as to present the frequency determiningvoltage to that element of the associated tuner. As before, channelselector 27 serves to drive the movable contacts associated withpotentiometer 53 from one channel selecting position to the next.

In practice, the channel selection contacts may be laid out on asubstrate more or less exactly as actually shown in FIG. 2 and thedifferent associated resistors may then be printed alongside thecontacts on the same substrate. Channel selector 27 then takes asuitable form for driving the movable contacts linearly along the arrayof fixed contacts. In order to achieve a more compact assembly, however,it is preferred to arrange the fixed contacts into a circle and use arotary switch mechanism to drive the movable contacts. This isillustrated in FIG. 3 wherein a plurality of channel positions appear assegments of an annulus numbered successively 2-83. Although not detailedin FIGJ3 for convenience of drawing, the individual fixed contactstructure at each channel position is like that shown in FIG. 2. Thatis, there is only a single contact segment at each of channels 2 and 83and the fixed contacts at the locations corresponding to channels 5, 7and 14 are divided into two segments. 1

The different fixed contacts preferably are printed upon a ceramicsubstrate which need be only about two inches square. Each contact areaor channel position may be assigned an arc of about 428 foraccommodating all 82 channels while permitting space between the channel2 and 83 positions for connecting conductors. The connecting conductorseach may be about 20 mils in width and spaced by the same amount whichdimensions are well within present day printed circuit capabilities.Also, all of the different resistors shown in FIG. 2 may in practice beprinted on substrate 130, generally adjacent to the respective differentfixed contacts. A representative number of these printed resistors areactually shown in FIG. 3. Thus, resistor 106 bridges the contactsassociated with channel positions 16 and 17, while resistor 107similarly bridges the positions corresponding to channels 15 and 16.Resistor 108 bridges the fixed contact positions corresponding tochannels 14 and 15, while resistor 109 extends from the one channel 14contact segment to an external connecting terminal 132 which in use, asindicated in FIG. 2, is to be connected to ground. Analogously, the onefixed contact segment associated with channel 13 is connected through aprinted resistor 1 12 to an external terminal 134 which, again asindicated in FIG. 2, is to be connected to B+. Similarly, the fixedcontact for channel 83 is connected through resistor 102 also to a 8+terminal 136. Step up resistors 120 and 123 bridge the separatedcontacts associated in moving between channels 6 and 7 and channels 4and 5, respectively. Finally, an external terminal 138 is connected by aprinted conductor to a central, circular conductive area 140, whileanother external terminal 142 is connected toan annular conductive area144 spaced around area 140. These last mentioned conductive areas serveconveniently in practice to make contact with ,movable .wiping contactsthat are driven by the channel selecting mechanism so as also to wipeacross the series of channel selection fixed contacts and therebycomplete selective connection to the latter. An example of this kind ofwiping contact arrangement will be shown in more detail in connectionwith FIG. a.

One formof channel selector mechanism is illustrated in FIG. 4. Alsoincluded in that Figure is a switch and resistor network 150 which,while shown in block diagram .form, is in this instance constructed inthe manner described in FIG. 3 so as to be selective as a rotary switch.The frequency determining voltage from network 150is fed to varactors 22and 24 of respective VHF .tuner and UHF tuner 21. At least basically,the electronic circuitry in FIG. 4 is the same as that shown in FIG. I;-in FIG. 4, however, the different control stages are lumped in one blockand denominated simply as a controlnetwork 151. Network 151 supplies B+to tuners 20 and 21 over respective leads 152 and 153,

'while feeding automatic-frequency control potentials to the respectivetuners over leads 155 and 156. Also, in the manner of switches 126 and128 of FIG. 1, network 151 is shown as including a band switch controllead 158 leading to tuner 20.

A fast-tuning means includes a first rotatable shaft 160 which may beturned by grasping a tuning knob 161. Shaft 160 is coupled to themovable selection contacts in the switch part of network 150 so as todrive those contacts from each one of the fixed contacts to the next.However, a first ball-detent 163 acts upon shaft 160 by means of aflange 164 which is rigidly affixed to shaft 160 and includes the detentseat. The detent acts to resist movement of shaft 160 each time uponmovement by the shaft of the switch selection contact successively overa chosen number of fixed contacts.

What maybe termed a slow-tuning knob 166 is secured on an end of asecond rotatable shaft 167. Mating spur gears 168 and 169 serve tocouple shaft 167 to shaft 160 by way of a flange ring 170 carried uponshaft 160 by a bearing 171 and, in turn, coupled to flange 164 by meansof the assembly including balldetent 163. Another ball-detent 173,carried between a rigid support 174 and a collar 175 affixed to shaft167, serves to detent shaft 167 in rotational increments that correspondto movement of the selection contact in network 150, through gears 168and l69'and shaft 160, from each one of the fixed contacts to the nextin the switch portion of network 150.

In designing and assembling the actual mechanical structure, each ofdetents 163 and 173 is caused to be reasonably stiff so that, forexample, when knob 161 is turned to rotate shaft 160, detent 163 yieldsbut detent 173 does not yield and shaft 167 and its knob 166 remainstationary. On the other hand, upon rotation of knob 166, overcoming thedetenting force of detent 173, that rotation is translated through thegear system, detent 163 and flange 164 to cause shaft to rotate; in thatcase, then, it is detent 163 which does not yield as detent 173 isforced to yield. Of course, it is the presence of the gear systembetween the two shafts whic permits such differential detent action.

In operation, knob 166 may be thought of as the VHF tuning knob, whileat the same time it also functions as a UHF slow-tuning knob. On theother hand, knob 161 serves as the UHF fast-tuning knob. That is, knob166 may be turned one channel at a time so as to tune throughthe VHFrange of channels 2 through 13 or through the UHF rangechannel-by-channel. On the other hand, the turning of knob 161 from anyone detent position on shaft 160 to the next causes an abrupt tuningchange past a group of successive channels. On reaching the end of thatgroup, the user may then again use knob 166 to move one channel at atime either upwardly or downwardly in the scale.

In one attractive arrangement, detent 173 has l2detent positions orpoints for each full rotation of shaft 167, corresponding to the 12 VHFchannels. At the same time, the ratio between gears 169 and 168 is sevento one, and detent 163 is selected to have seven detent points forrotation of shaft 160. Consequently, knob 161 becomes a fast-tuning knobdetented every twelve channels. When knob 166 is turned, starting atchannel two, the VHF channels are tuned in ascending order until 13 isreached. If knob 161 is then advanced, the tuning jumps twelve channels,first to channel 26, then to channels 38, 50, 62 and 74, and finallyback to VHF channel 2 again. When the user desires to go from, say,channel 14 to channel 20, VHF knob 166 maybe rotated by in order tocover the six chan nels involved. Alternatively, channel 20 also couldbe tuned by using UHF knob 161 and turning it one detent so as to jumpfrom channel 14 to channel 26 after which VHF knob 166 would then beused to turn backwardly six individual channels.

In use, it is apparent that the successive UHF channel numbers mayconveniently be distributed around the periphery of knob 161, while theVHF channel numbers are similarly distributed around the periphery ofknob 166. By making those peripheries transparent or at leasttranslucent, an indicator lamp 178 may be disposed behind the peripheryof knob 161 to illuminate the selected UHF channel number. Similarly, anindicator lamp 179 disposed behind the periphery of knob 166 may beilluminated to indicate the selected VHF channel. To this end, oneterminal of each of lamps 178 and 179 is connected to ground while theirother terminals are individually connected to respective fixed contacts180 and 181 of a single-pole, double-throw switch that includes amovable armature 182 connected to an A+ potential source for energizingthe lamps. Armature 182 is moved by a suitable cam, indicated by dashedline 183, carried by flange 164 so as to effect energization of lamp 178whenever shaft 160 is in the portion of its rotation corresponding toUHF switch contact selection. On the other hand, lamp 179 is energizedduring the other portion of the rotation of shaft 160 when VHF switchcontacts 180 and 181 also are connected through leads 185 and 186,respectively,

to control network 151 so as to provide the necessary shaft 167 andtheratio between gears 168 and169 is 14 to 1 while detent 163 has fourteendetent points. In thatcase, there still are 84 total detent or switchpoints uponrotation of knob 166, but the number of channels jumpedbetween each detent upon rotation of shaft-160 is reduced to six. Stillother cor'nbinations'are possible. For examplegdetent 173 may beassigned-ten detent points for'each rotation of shaft 167, with theassigned gear ratio being changed so that it is nihe to one and detent163 having nine pointsxln that case, the number of channels jumped uponeach detent of knob 161 is ten. Also, the number of total points ofrotation of shaft 160 then is 90, so that a few additional unused pointsexist.

In FIG. 4, shafts 160 and 167 are parallel to one an other and spacedapart so that entirely separate knobs 161 and 166 are appropriate.However, the coaxial knob and shaft arrangement of FIGS. 51-5e offersthe advantage of a more compact and convenient overall channel selector.In this case, a UHF or fast tuningknob 190 is coupled through spur gears191 and 192 directly to a fast-tuning shaft 193 that drives the movableswitch contacts in network 150. As illustrated, a switch contact 195 iscarried by shaft 193 to wipe central area 140 (FIG. 3), while anothermovable contact 196 electrically connected to contact 195 is positionedto rotate over and thus wipe successive ones of the individual differentfixed switch contacts distributed in an annular ring as shown in FIG. 3.Although not specifically shown in FIG. a, a second contact pair alsopreferably is carried on the rearward end of shaft 193 in order towipingly connect annular ring 144 to the array of fixed contacts andthus complete the arrangement for connecting both ends of potentiometer52 simultaneously across adjacent fixed contacts.

A VHF or slow-tuning knob 200 is coupled, through a gear systemcontaining a spur gear 201 and another spur gear 202 together with adetent 203, to shaft 193. Also on the shaft carrying knob 200 and gear201 is another detent 205. Detent 205 is of a simple ball and riphand,and as detailed in FIGS. 5c'5e, detent 203 includes a ball 208 which maybe received in any of a plurality of seats 209 distributed around onelateral face of a hub integral with shaft 193. A spring 210 riveted atone end to gear 202 and retained in place by a C- washer 211 yields uponthe turning of knob 190 so as to permit shaft 193 to be turned while yetnot. causing knob 200 to be changed through gears 202 and 201. On theother hand, upon the application of a turning force to knob 200, detent205 yields so that shaft 193 is driven by way of gears 201 and 202; inthis case, it is detent 203 which does not yield.

Fixedly secured to the rear face of knob 190 is an indicator disc 215.For the case in which detent 203 has nine rotary positions, detent 205has rotary posi tions and the ratio between gears 202 and 201 is nine toone, the face of indicator disc 216 conveniently is divided into ninesegments each containing 10 equal spaces. All of the different channelsmay then be distributed in order around the periphery of disc 215 so asto be indicated by a pointer 216. As before, knob 190 causes fastrotation and turns one-ninth of a revo- V .lution for each d tent.

Rotation of knob 200 causes shaft 193 to rotated. by one; increment orchannel point at a time Alternatively, 't'heother detent andgearratiopombinations previously explained may be ple d wafer typeconstruction as shown. On the other channels, .whether-UHFor VHF, have the same ease 'of accessibility and indication upon using kn0b- 00andreading thewchannel. number oftltheface of disc 215. Yet, therother knob.190 offers the user; the additional flexibility of being able rapidlyto get from one place in the channel series to a .widely separatedplace.

The various arrangements described,. therefore, en-

. able the arrangement of a television. channel selector so as to) have,improved, ease and accuracy of tuning and indication. When desired,access to different adjacent channels in both the UHF and VHF regionsmay be achieved by manipulation of but a single tuning knob. At the sametime, however, rapid access also is provided to widely separatedchannels. As best illustrated in FIG. 3, advantage is taken of printedcircuitry for achieving compact and yet convenient switch action andselection. Moreover, the different arrangements permit use of a singlefine tuning control in both the UHF and VHF regions.

While particular embodiments of the present invention have been shownand described, it is apparent that changes and modifications may be madetherein without departing from the invention in its broader aspects. Theaim of the appended claims, therefore, is to cover all such changes andmodifications as fall within the true spirit and scope of the invention.

What is claimed is:

1. A combined UHF and VHF television channel selector comprising:

tuning means including a plurality of varactors as the frequencydetermining elements, the frequency determined being a function of thevoltage presented to a respectively terminal of each such varactor;

a rotary switch having a predetermined number of fixed contactsrespectively associated with different channels in the VHF and UHftelevision spectra and at least one selection contact movable overrespective different ones of said fixed contacts;

a voltage divider composed of a plurality of resistors series connectedin succession with individually progressive different junctions betweensaid resistors connected to respective different ones of said fixedcontacts;

means for impressing a D-C potential across said voltage divider;

fast-tuning means including a first rotatable shaft coupled to saidselection contact for driving the same from each one of said fixedcontacts to the next;

means for detenting said first shaft each time upon movement of saidselection contact successively between a chosen number of said fixedcontacts, said number being greater than two slow-tuning means includinga second shaft;

a gear system mechanically coupling said second shaft to said firstshaft;

means for detenting said second shaft in rotational incrementscorresponding to movement of said selection contact, through said gearsystem and said first shaft. from each one of said fixed contacts to thenext;

and means for selectively coupling said selection contact to each ofsaid varactors for establishing a tuning frequency. 2. A selector asdefined in claim 1, which includes an indicator wheel affixed to saidfirst shaft and having a plurality of channel indicating numbers,corresponding 'to selection of respective different ones 'of said'fixcdcontacts, successively spaced around its periphery.

through said means for detenting said first shaft and in which, uponoperation of said fast-tuning means, said means for detenting said firstshaft yields without yielding of said means for detenting: said secondshaft.

6. A selector as defined in claim 5, in which, upon operation of saidslow-tuning means, said means for detentingsaid second shaft yieldswithout yielding of said means for detenting said first shaft.

7. A selector as defined in claim 2, in which said VHF spectra hastwelve channels and in which said means for detenting said second shafthas a number of detents for one complete rotation of said second shaftwhich is integrally divisible into 12.

1. A combined UHF and VHF television channel selector comprising: tuningmeans including a plurality of varactors as the frequency determiningelements, the frequency determined being a function of the voltagepresented to a respectively terminal of each such varactor; a rotaryswitch having a predetermined number of fixed contacts respectivelyassociated with different channels in the VHF and UHf television spectraand at least one selection contact movable over respective differentones of said fixed contacts; a voltage divider composed of a pluralityof resistors series connected in succession with individuallyprogressive different junctions between said resistors connected torespective differEnt ones of said fixed contacts; means for impressing aD-C potential across said voltage divider; fast-tuning means including afirst rotatable shaft coupled to said selection contact for driving thesame from each one of said fixed contacts to the next; means fordetenting said first shaft each time upon movement of said selectioncontact successively between a chosen number of said fixed contacts,said number being greater than two slow-tuning means including a secondshaft; a gear system mechanically coupling said second shaft to saidfirst shaft; means for detenting said second shaft in rotationalincrements corresponding to movement of said selection contact, throughsaid gear system and said first shaft, from each one of said fixedcontacts to the next; and means for selectively coupling said selectioncontact to each of said varactors for establishing a tuning frequency.2. A selector as defined in claim 1, which includes an indicator wheelaffixed to said first shaft and having a plurality of channel indicatingnumbers, corresponding to selection of respective different ones of saidfixed contacts, successively spaced around its periphery.
 3. A selectoras defined in claim 2, in which said first and second shafts are spacedapart and parallel to one another.
 4. A selector as defined in claim 2,in which said first and second shafts are coaxial,
 5. A selector asdefined in claim 2, in which said gear system couples said second shaftto said first shaft through said means for detenting said first shaftand in which, upon operation of said fast tuning means, said means fordetenting said first shaft yields without yielding of said means fordetenting said second shaft.
 6. A selector as defined in claim 5, inwhich, upon operation of said slow-tuning means, said means fordetenting said second shaft yields without yielding of said means fordetenting said first shaft.
 7. A selector as defined in claim 2, inwhich said VHF spectra has twelve channels and in which said means fordetenting said second shaft has a number of detents for one completerotation of said second shaft which is integrally divisible into 12.